Correct

开小差

/ kāixiǎochāi / 
Strokes

Definition

to be absent-minded/to desert/to abscond from the army/absent without leave (AWOL)

Example

As a Verb

(of a soldier) desert

1
Yǒuxiē
有些
shìbīng
士兵
zài
在
zhànzhēng
战争
zhōng
中
kāixiǎochāi
开小差
  
。

Some soldiers deserted in the combat.

As a Verb

be absent-minded; be woolgathering

2
Gāng
刚
shàngkè
上课
tā
他
jiù
就
kāishǐ
开始
kāixiǎochāi
开小差
le
了
  
。

His mind wandered soon after the class began.